TO <-> TC4400 Modem speed / configuration problem - SOLVED

I want to replace my aging Cisco EPC3212 cable modem with a new Technicolor TC4400 cable modem (latest firmware). When I measure the speed with a laptop directly connected to the TC4400 the speed is fine.

But when I connect the TO to the TC4400 the internet speed is very poor. Latency is ok. Data in ethtool -S eth0 and eth1 looks ok. Link between modem and TO looks good too.

SOLVED: The cause for this speed issue was the CAT-5 cable length between the modem and the TO. It had nothing to do with the TO. Compared to my previous Cisco and Ubee cable modems, the TC4400 has a very weak WAN signal. I installed a switch in the middle between the modem and the router to fix this issue.

And length CAT-5 Cable between modem and TO?